The present invention relates to calenders in general, and more particularly to improvements in means for supporting certain rolls of the roll train in a calender. Still more particularly, the invention relates to bearings for calender rolls and to supports for such bearings, especially to bearings for the lower or lowermost roll of a train which contains at least two rolls.
It is known to mount a roll train in the spaced apart uprights of a roll stand through the medium of bearings which are movable along guides on the respective uprights. It is also known to provide such calenders with hydrostatic motors or analogous means for moving one of the outermost rolls, normally the lowermost roll of a roll train wherein the rolls are disposed one above the other, against fixed stop means so as to ensure that the one outermost roll is fixed in a selected position when the calender is in use. The bearings for the one outermost roll have surfaces which are parallel to and slide along guide faces on the respective guides. Reference may be had to U.S. Pat. No. 2,861,504 which discloses that motors in the form of cylinder and piston units serve to allow for rapid lowering of the lowermost roll or of two or more lower rolls of a roll train wherein the rolls are disposed one above the other. The bearings for the lowermost roll or rolls extend into spaces between two parallel columns of the stand, and the columns have stops against which the bearings of the lowermost roll abut in the raised position of the lowermost roll. Such mounting of bearings for the lowermost roll cannot ensure wobble-free retention of the lowermost roll in a given position.
German Auslegeschrift No. 20 10 322 discloses a calender with a substantial number of intermediate rolls between the uppermost and lowermost rolls of the roll stand. The uppermost roll is biased downwardly by a cylinder and piston unit. The stand is located at one side of the roll train and is provided with guides for the bearings of the rolls. The bearings have surfaces which abut against complementary guide faces of the guides. The guides are vertical and resemble ribs the front sides of which are contacted by the surfaces of the bearings. The bearings for the lowermost roll of the roll train are mounted differently, namely, each such bearing is disposed between two guides located at the opposite sides of the vertical plane including the axis of the lowermost roll. The part which determines the uppermost position of the lowermost roll when the calender of this German publication is in use is provided on top of the cylinder of the cylinder and piston unit which serves to lift the lowermost roll.
The aforediscussed conventional calenders share the drawback that the bearings for the lowermost roll are free to move in a horizontal plane when the calenders are in actual use. This is due to the fact that such bearings are merely slidable along the corresponding pairs of guides but cannot be locked against horizontal movement once the lowermost roll reaches its operative position. It has been found that the bearings for the lowermost rolls in such conventional calenders can move in the axial direction as well as at right angles to the axis of the lowermost roll. This leads to pronounced vibrations in a horizontal plane and attendant periodical changes in the width of the gap between the lowermost roll and the roll immediately thereabove. Vibrations of the just outlined character adversely affect the quality of the treated webs and cause pronounced wear upon the parts of the machine. Furthermore, vibrations of the lowermost roll are communicated to the cylinder and piston unit or units which serve to lift the lowermost roll to operative position so that the seals between the pistons or plungers and cylinders of such units are destroyed and the pressurized fluid is free to escape from the cylinder chambers. The intensity and extent of the just discussed vibrations of the lowermost roll is increased with increasing rotational speed of the rolls, i.e., with increasing output of the calender.